SECONDARY ANTIPROTON SPECTRUM IN THE ATMOSPHERE WITH THE INCLUSION OFFERMI MOTION IN AIR NUCLEI

A calculation is made to estimate the secondary antiproton ((P) over b ar) spectrum in the atmosphere by the interaction of cosmic rays. Ferm i motion of target nucleons has been included for the first time in th e determination of the production of (P) over bar s. As a result, the production of (P) over bar is higher than the earlier estimates below a few GeV, which increases with decreasing energy of (P) over bar, and is about a factor 7 at 100 MeV. The energy spectra of (P) over bar an d (n) over bar are determined as a function of atmospheric depth by ta king into account all energy loss processes. The calculations show tha t the spectral shape of secondary (P) over bar s below about 2 GeV evo lves rapidly over the entire atmosphere. The derived spectra at small depths are useful to make corrections for (P) over bar s produced in t he overlying atmosphere in balloon borne experiments, which are design ed to measure the energy spectrum of primary (P) over bar s. The secon dary (P) over bar/P ratio varies from about 10(-7) at 50 MeV to 4.5 x 10(-3) at 100 GeV. A method is also suggested to make corrections in e xperiments, in which the (P) over bar/P ratio can only be determined. A comparison is made with the earlier estimates and the suggestion is made to test the results of this calculation using ground based experi ments.